1. Technical Field
This invention relates to thin film metal alloy magnetic recording disks for horizontal recording, and in particular to a CoPt alloy or CoNi alloy disk having low intrinsic media noise at high linear recording density.
2. Description of the Prior Art
One of the problems with thin film metal alloy media, including CoPt alloy and CoNi alloy media, is that the intrinsic media noise increases with increasing linear recording density. Media noise arises from irregularities in the magnetic transitions and results in random shifts of the readback signal peaks. These random shifts are referred to as "peak jitter" or "time jitter". Thus, the higher the media noise, the higher the bit error rate. It is therefore desirable to develop a thin film metal alloy media which generates noise below a maximum acceptable level in order that data can be recorded at maximum linear density. The effect of intrinsic media noise, as measured by peak jitter and media signal-to-noise ratio (SNR), on the bit error rate in magnetic recording systems is described by Katz, et al., in "Effect of Bitshift Distribution on Error Rate in Magnetic Recording", IEEE Trans. on Magnetics, Vol. MAG-15, pp. 1050-1053, 1979. The measurement of media SNR is described by Belk, et al., in "Measurement of the Intrinsic Signal-to-Noise Ratio for High Performance Rigid Recording Media", J. Appl. Physics, 59 (2), Jan. 15, 1986, pp. 557.562.
Assignee's U.S. Pat. No. 4,789,598 describes a CoPtCr metal alloy magnetic recording disk wherein the high Cr concentration reduces the intrinsic media noise at high recording density.